Presence of anchovy in acoustic research surveys PELACUS 2001-2005

Abstract

The research survey PELACUS started at the 80s, particularly since 1983, and from 1986 onwards is a spring survey. Although it changed its name from time to time it has always been the northern Spanish acoustic research survey. Its main aim is the assessment of pelagic resources by acoustics tools across the northwest and northern Spanish waters. This survey is mainly targeted at sardine, although other pelagic resources are also taken into account, such as horse mackerel, mackerel and anchovy. The sampling area comprises the northern part of Portugal (ICES area IXa Central North), in the vicinity of Porto and extends to the southern Atlantic French waters (ICES area VIIIb), in the vicinity of Arcachon. Depths are from 30 to 200 m. The acoustic device is an echosounder EK-500, working at frequencies of 12, 38 and 120 KHz. This echosounder was replaced in 2005 by a new echosounder EK-60, working at frequencies of 18, 38, 70 and 120 KHz. Fish samples were collected by a pelagic trawling gear, with 24 m of vertical opening. An auxiliary purse-seiner is also chartered to help in shoal identification in coastal waters. This fishery boat is mainly used when the research vessel cannot fish because of the bathymetry, particularly in the Rias Bajas area, in Galicia. The presence of anchovy was rather occasional in PELACUS and no assessment is routinely produced because of the poor presence of this species on fishing samples as well as echograms. Also it has to be considered that this survey is mostly targeted to sardine and both ICES WGMHSA Report 2006 611 the distribution area and the main season of abundance of anchovy are not totally covered by this survey. Hence the research surveys PELACUS are considered NOT GOOD INDICATORS on anchovy distribution and abundance and conclusions regarding anchovy from this survey should be taken with caution.